Following are some acronyms used in the description of the invention:
3GPP third generation partnership project
CCE connection control entity
DL downlink
eNB. evolved Node B (base station of an LTE network)
E-UTRAN evolved universal terrestrial radio access network.
FDD frequency division duplex
H-ARQ hybrid automatic repeat request
LTE long term evolution (also known as E-UTRAN or 3.9G)
PHICH physical H-ARQ indicator channel
PDCCH physical downlink control channel
PRB physical resource block
TDD time division duplex
TTI transmission time interval
UE user equipment
UL uplink
Relevant to these teachings is the H-ARQ behaviour in connection to measurement gaps. One of the central features of LTE is the usage of fast hybrid automatic repeat request (H-ARQ), which is used to increase the spectral efficiency. The normal H-ARQ operation for dynamic scheduled uplink data is that that for each uplink resource grant [which is signalled on the downlink control channel (PDCCH)], there will be an associated H-ARQ feedback channel for positive (ACK) and negative (NAK or NACK) acknowledgements. In the current understanding in 3GPP, there will be a delay between the time of the uplink grant (which is sent on the PDCCH) to the time where the UE will actually transmit uplink data, and a further delay to the time where the eNB should send the ACK/NACK on the PHICH (physical H-ARQ indication channel). The current assumption is that the scheduling delay will be 3 ms (plus the delay of the actual signalling on the PDCCH), and that the eNB processing time will also be 3 ms. This means that the timing relation for a single H-ARQ process or channel will be (by example) according to the following sequential TTIs:                TTI#0: UL allocation grant is sent on the PDCCH.        TTI#4: UL data transmission from the UE on the granted UL resource.        TTI#8: ACK/NACK is sent on the PHICH [or a dynamic scheduling for a retransmission on the PDCCH in the case of adaptive H-ARQ].        
Consider the case where non-adaptive H-ARQ is used for the uplink (meaning that uplink retransmissions are performed on the same physical resources, and the UE only needs an indication of whether it should do a retransmission in the uplink). This is handled through PHICH signalling, where under current understanding in 3GPP the UE will be assigned a PHICH resource through its ‘allocation order’, which for instance could be related to the CCE index used for the indication of the resource allocation (TTI #0 in the above sequence). Another method is to relate the allocation order to the assigned uplink physical resources combined with additional signalling to indicate an offset relative to the first PRB index of the allocated physical resources.
In the RAN4 group of 3GPP development, discussions are currently ongoing as to when and how to allow for the UE to do measurements (including cell identification and signal level measurements) related to handover. It is understood that the UE needs to do cell identification and additionally some measurements of the channel (i.e., some measure of channel quality such as signal strength) with neighboring eNBs to be prepared for handover from one eNB to another. This is termed in 3GPP a measurement gap, the time at which the UE is performing cell identification of surrounding cells (inter-frequency or inter-radio access technology RAT) and taking measurements in order to report same (generally for handover purposes but they may also be imposed by the eNB for network configuration or testing or other more routine purposes). This measurement gap will occur at time instants that are coordinated between the eNB and the UE. But it is clear that these measurement gaps will influence or break the H-ARQ timing relationships.
The current agreement on this matter in 3GPP is captured in the latest changes to E-UTRAN stage 2 specification 36.300, which can be seen at document R2-075484 (Change Request, 3GPP TSGRAN2 Meeting #60, Jeju, South Korea, 5-9 Nov. 2007 by Nokia Siemens Networks):                Measurement gaps are of higher priority than H-ARQ retransmissions: whenever an H-ARQ retransmission collides with a measurement gap, the H-ARQ retransmission does not take place.As such, there is an awareness that these measurement gaps will occur and conflict with H-ARQ communications, and it is determined that where there is a H-ARQ transmission to take place while the UE is within a measurement gap, the H-ARQ transmission will not take place. This is a simple implementation because the eNB knows the measurement gap (and generally commands it of the UE) and the eNB also knows when it is to send the ACK/NACK to that same UE, so the eNB simply foregoes sending its ACK or NACK to the UE according to the above priority decision agreed for LTE.        
This agreement basically means that a measurement gap is truly a gap in which the eNB cannot expect the UE to receive any DL information, including PDCCH or transmit any information in UL including H-ARQ ACKs and NACKs.
The inventors are unaware of any solution proposed by another. One straightforward option that avoids the problem is to equip the UEs with two transmitters and two receivers. But apart from increasing costs of UEs and failing to account for legacy UEs already in use that do not have such dual transceiver capacity, the design of such a UE is not a simple matter as simultaneous transmission and reception to/from the same device, using frequency division to divide the signals, can raise interference problems internally within the UE.
What is needed is a way to enable H-ARQ where the normal H-ARQ timing would occur within a measurement gap and without waiting so long as to make the H-ARQ effectively worthless (e.g., interpreted as non-reception due to the passage of a threshold time period).